Quality consistency inspection Quality consistency inspection is also called settlement inspection and factory inspection. The purpose of the test is to use as simple as possible a method that is both economical and reflects actual use, and randomly samples the fasteners to meet the corresponding product standards, as a basis for determining whether the batch can be accepted. Generally speaking, the quality consistency inspection project is less than the qualification inspection, but for the fasteners with less inspection items and simple test, the items of the two inspections can be identical. In this case, a quality consistency test can be used instead of an identification test.
In order to ensure representativeness of the test results, production batches and inspection lots must be defined. A production batch is a finished fastener that is put in or produced at one time. These fasteners must be manufactured from the same batch of material, manufactured in the same process, heat treated in the same furnace, and the fasteners are of the same type and size. Inspectionlots are a number of finished fasteners that are assembled to perform a sampling inspection. For fasteners requiring heat treatment, one inspection lot must be from the same production batch and submitted by the manufacturer at one time. A production batch can be divided into several inspection lots or as an inspection lot.
Re-inspection into the factory for re-inspection is a supervised sampling test of the quality of fasteners purchased by users. According to the requirements of the general quality management system, all purchased products (excluding homemade products) must be re-examined, otherwise the income pool cannot be verified. The general content of the re-inspection of the factory includes quality certification documents, appearance, re-inspection of dimensions and re-inspection of basic performance. The re-inspection of the quality certification documents is mainly to check the certificate of the fasteners, especially the batch number or the date of manufacture of the fasteners to ensure the traceability of the fasteners. In addition, check the fasteners, signs and quantities to ensure consistency between the received product and the contract. The appearance and size re-inspection is mainly to check the surface quality of the fastener, the coating layer and the important dimensions, such as the thread precision of the threaded fastener, the diameter of the shear fastener, and the like. Basic performance re-inspection is a mandatory requirement for aerospace systems at specific times.
The inspection batches of fasteners are generally large, and the production process can also be regarded as continuous production. However, in order to ensure the quality of each batch of fasteners, the sampling plan is selected according to the isolated batch, and batch-by-batch inspection is required. Commonly used inspection programs have a counting sampling plan and a secondary sampling plan.
The appearance and size inspection of fasteners generally adopts a one-time sampling plan, which can be calculated according to the number of unqualified products per hundred units of products, or the number of defects per hundred units of products. According to the degree of importance of defects, they are usually divided into fatal defects, heavy defects and light defects, which respectively specify different acceptable quality levels (AQL). For example, cracks are generally fatal defects, and their AQL value is 0.065. The more important dimensions (such as thread, surface roughness, bolt diameter, etc.) AQL value is 1.0, and the minor size is 4.0.
It is often given that LQ 10 is not a requirement of the sampling procedure, but rather tells the ordering party the risk of adopting the scheme. The ultimate quality is related to the acceptable quality level (AQL), ​​sample size (n) and ordering party risk. When the fastener has AQL=1.0, the sample size is 80, and the acceptable judgment number is 2, the ordering party risk is 10%. It can be found from the GJB179A table that the limit mass at this time is 6.52. It means that when sampling with (80,2) scheme, the acceptance probability is 10% when the limit quality is 6.52; if the ordering party risk is 5%, then the batch The receiving probability of the limit mass of 7.66 is 5%, that is, LQ 5 = 7.66.
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